Real world cloaking device?

Cloaking 2.0
There was a “you’ve got to be kidding me” moment back in 2006 when Duke University researchers announced that they had developed a cloaking device that could make objects invisible – at least to microwaves – using a metamaterial system composed of concentric circles of circuit boards that guide the waves around an object placed in their center. In theory, the method also could be used to manipulate any electromagnetic radiation such as light around an object, in effect making it invisible in two dimensions. Now, two groups have published near-simultaneous articles that expand on these concepts, adding acoustic invisibility and “perfect” light absorption.

A group of engineers from the Polytechnic University of Valencia (Spain), building on the light cloaking theories, have recently published plans for making a structure of sonic crystals containing small cylinders of materials like aluminum. This crystalline structure would guide sound waves around an object and allow them to re-form and continue.

Although the actual effort to create an acoustic cloak faces some tall engineering hurdles, the benefits and applications could be widespread. Lead engineer José Sanchez-Dehesa told the MIT Technology Review that it should be possible to create a cloak of any size and shape. This type of super-stealth technology would have obvious military applications such as making ships invisible to sonar and radar, but peaceful uses would also be widespread. Sanchez-Dehesa said that it would be possible to create homes and office buildings that are impervious to outside noises and concert halls with support columns that would not block or distort sounds. An acoustic cloak would not be restricted to a single frequency, a problem that limits the practical applications of a light cloak.

The second group, which includes researchers from Boston College plus some of the same engineers at Duke who developed the original light cloak, appear to have created another stealth technology by creating a perfect light sponge. The term “perfect” is not thrown around lightly. The group claims that the geometric surfaces of certain metamaterials can be crafted to seize all of the electromagnetic properties of light and convert the energy into heat. No light is reflected or transmitted. Again, military applications seem obvious, but so, too, are applications related to increasing the efficiency of solar heaters and similar devices.